Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
1999-10-04
2001-08-07
Kwon, John (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
C060S285000
Reexamination Certificate
active
06269793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates reciprocating internal combustion engines having individual cylinder fuel control and camshaft timing control.
2. Disclosure Information
In the interest of reducing fuel consumed by automotive engines, it is desirable to shut off fuel delivery when the engine is decelerating. This is termed deceleration fuel shut off (DFSO). A problem with such deceleration arises with respect to engines having exhaust aftertreatment systems, however. If fuel is shut off to an engine during deceleration, but the airflow through the engine continues unabated, the aftertreatment system will become loaded with oxygen and this will cause an excess amount of oxides of nitrogen (NOx) to be released once normal combustion is resumed. Unfortunately, even with the throttle in its closed or idle position, enough air will leak past and thereby cause the undesirable oxygen loading problem. And, although it is known to use port throttles and limited camshaft timing changes to control the gas flow through an engine during certain operating conditions, such a scheme will not work for the purpose of preventing the previously described NOx spike, because port throttling will allow some air to pass through the engine's cylinders, thereby loading the exhaust after treatment device with oxygen and causing the previously described increase in NOx when the engine is reactivated following a deceleration.
A system according to the present invention allows fuel to be shut off during engine deceleration without causing an increase in NOx during reactivation of the engine, because the engine's camshaft or valve timing is changed to the extent that regardless of the position of the engine's throttles, no net flow of mass, whether it be air, exhaust, or otherwise, will flow through the engine. In effect, charge is trapped in the engine and charge flow is halted.
SUMMARY OF THE INVENTION
A multicylinder internal combustion engine according to the present invention includes a crankshaft, a plurality of cylinders with each having a piston reciprocably mounted therein and connected to the crankshaft for reciprocation, and a plurality of intake and exhaust poppet valves for allowing intake air to enter the cylinders and for allowing combustion products to leave the cylinders. The intake and exhaust valves are powered by either a camshaft connected with a phaser which controls the timing of the camshaft, or by another type of valve actuation system which is capable of opening and closing the poppet valves according to a timing pattern established by a controller. The controller operates the intake and exhaust poppet valves either by means of the phaser or by another valve actuation device. The controller also operates fuel injectors which supply fuel to the cylinders.
When an engine equipped with a system according to the present invention decelerates in speed, the controller will reduce the flow of fuel to the cylinders and adjust the timing of the camshaft or other valve actuating system such that there is no net flow of charge through the cylinders and no fuel entering the cylinders. In the event that a dual equal camshaft timing system is used, such as with an engine having either a single camshaft for driving the intake and exhaust valves of a cylinder bank or separate camshafts which are driven according to the identical timing, the camshaft timing will be retarded such that the exhaust valves open after bottom dead center of the power stroke of the cylinder in which any particular exhaust valve is situated. Said another way, the opening and closing of the intake valves will occur approximately symmetrically about bottom dead center of the intake stroke and opening and closing of the exhaust valves will occur approximately symmetrically about top dead center of the exhaust stroke.
In the event that intake timing change only is used with a system according to the present invention, the intake poppet valve timing will be advanced such that the opening and closing of the intake valves occurs approximately symmetrically about top dead center at the conclusion of the exhaust stroke. In the event that exhaust only timing change is used according to the present invention, the timing of the exhaust poppet valves will be retarded such that opening and closing of the intake and exhaust valves occurs approximately concurrently and symmetrically about the midpoint of the intake stroke.
For the purposes of this specification, the engine is assumed to be a conventional four-stroke cycle reciprocating internal combustion engine.
According to another aspect of the present invention, a method for operating a poppet valve equipped, multicylinder internal combustion engine having a catalytic aftertreatment device, so as to avoid cooling and oxygen loading of the catalyst during deceleration fuel shut off, comprises the steps of: 1) sensing deceleration of the engine; 2) shutting off fuel supply to the cylinders of the engine; and 3) simultaneously with shutting off the fuel, adjusting the timing of the poppet valve opening and closing events such that no net flow of gases to and from the cylinders occurs.
It is an advantage of the present invention that an engine equipped with the present system will save fuel.
It is a further advantage of an engine according to the present invention that increased engine braking will be available with certain applications of this system.
It is yet another advantage of an engine according to the present invention that decreased engine-out exhaust emissions will be generated.
Other advantages as well as objects and features of the present invention will become apparent to the reader of this specification.
REFERENCES:
patent: 5119781 (1992-06-01), Trombley et al.
patent: 5515824 (1996-05-01), Yamagishi et al.
patent: 5558051 (1996-09-01), Yoshioka
patent: 5884476 (1999-03-01), Hirota et al.
patent: 5921078 (1999-07-01), Takaku et al.
Russ Stephen George
Stockhausen William Francis
Drouillard Jerome R.
Ford Global Technologies Inc.
Kwon John
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